Electric fuse



June 6, 1933' LA MAR 1,913,163

ELECTRIC FUSE Original Filed June 21, 1926 QM 'aYserazM KWTN EY Patented June 6, 1933 UNITED STATES PATENT OFFER FRANK C. LA MAR, OF NEW YORK, N. Y., ASSIGNOK TO GREAT ESTERN FUSE CO. INC., OF PITTSBURGH, PENNSYLVANIA, A CORPORATION DELAWARE nrnornrc FUSE Continuation of application Serial No. 117,403, filed June 21, 1826. This application filed June 8, 1929.

Serial No. 389,405.

This invention relates to fuses, especially electric fuses of the enclosed type and more particularly to fuses of this type in which there is a terminal projecting from each end of the fuse.

It is well known to those familiar with the fuse art that a fuse may be constructed by taking two terminals, preferably of the knife blade form, and connecting them by means of a fusible link. Such a device would well serve to interrupt an electric circuit in which it had been interposed when an overload or excessive flow of current occurred in such circuit. When the fusible link is fused by an excessive flow of current the metal of the fusible link is fused and melted and practically volatilized with the production of hot gas and flame. The hot metal is thrown and the flame plays on surrounding objects. In order to protect surrounding objects from injury by this .hot metal and flame the fusible link may be sur' rounded by an enclosing body. Ordinarily, even when an enclosing body is used the heat and flame generated by the melting and combustion of the fusible link shoot out at each end of the surrounding body and have at least a potential ability for doing considerable damage to surrounding obiects. The enclosing body cannot be sealed absolutely gas-tight because when the fusible link or element is fused by the excessive flow of current such a gaseous pressure is generated that the enclosing body would be blown apart. It is necessary, therefore, to provide some sort of a vent so that the gaseous pressure within the enclosing body may be relieved quickly enough to avoid a destructive act on upon the body or case. T 0 allow the hot gases or flame to issue from the enclosing body or case along the faces of the knife blade terminals is highly objectionable because they are thereby guided directly against the terminal clips in which the knife blades are placed. It is, therefore, desirable to relieve the gaseous pressure generated within an enclosed fuse by method which will prevent the hot gases and flame from being guided directly toward any nearby surrounding object such as clips in which the knife blade terminals are usually placed, and to cool the as before it issues to atmosphere.

A principal object of this invention is to provide a construction for a fuse of the type described in which the hot gases and flame generated by the fusing and combustion of a fusible link or element will'be allowed to gradually flow to the surrounding atmosphere along a path which will carry them away from the nearby terminal or knife blade clips. I

A further object of the invention is to so construct a fuse of the type described that the gases and flame will be directed through a substantially elongated path or channel before being allowed to flow to atmosphere.

A. further object of the invention is to somewhat cool the gases before they are dis charged into the atmosphere.

A further object of the invention is the construction of a fuse of the type described of such form that the hot molten metal caused by the fusing of a fusible element will not solder the parts of the fuse together.

Further objects and advantages will appear as the description of the particular physical embodiment selected to illustrate the invention progresses and the novel features of the invention will be particularly pointed out in the appended claims.

In describing the invention in detail and the particular physical embodiment selected to illustrate the invention reference is had to the accompanying drawing in which like characters of reference designate corresponding parts throughout the several views, and in which:

Figure 1 is a plan view of a fuse embodying applicants invention with certain parts broken away and other parts separated to more clearly show the construction; Fig. 2 is an enlarged plan view of one end of the fuse as shown by Fig. 1 with certain parts broken away to more clearly show the construction; Fig. 3 is an end view of the fuse, as shown by Fig. 1, but with certain parts removed to more clearly show the end construction and with dotted lines indicating a position of one of the parts during the process of assembly; Fig. 4 is an enlarged detail plan view of one of the knife blade terminals and a closure washer together with a fragment of fusible link; Fig. is a perspective view of a knife blade terminal with its associated flange as used in applicants invention Fig. 6 is a separated view of a knife blade terminal and its associated flange as used in applicants invention.

For the purpose of explaining the principles and construction of my improvement in fuses I have illustrated the usual fusible link 1 in the drawing. This fusible link may be of the ordinary and well known forms. In accordance with usual custom the fusible link 1 is attached by means of the screw fastenings 2 to end terminals 3 and 4. These end terminals may be of any desired or appropriate form but are shown as of the knife blade type because peculiarly adapted for insertion in the ordinary and well known clips usua ly used in connection with fuses of the type to which my invention particularly relates.

The link 1 together with the terminals 3 and 4 constitute a complete fuse but for the reasons hereinbefore pointed out it is both desirable and necessary, because of the formation of hot gases and flame generated by the combustion of the fusible link 1 due to an overload or excess flow of current, to e11- close the fusible link 1 so as to prevent injury to adjacent objects.

For the purpose of illustrating my improvement I have selected a well known form of surrounding body or cartridge 5. This cartridge 5 may be of any suitable or appropriate form but is preferably in the form of a hollow cylinder, as shown in the drawing, and is constructed of an insulating material, preferably, hard, dense fibre.

In order to provide a fastening for conveniently and properly closing the ends of the cylindrical body 5 I have illustrated the well known ferrules as 6 and 7 on each end of the body 5. These ferrules in practice, although not necessarily so, are identical in construction and for the purpose of explaining my improvement I prefer to illustrate these ferrules as being identical in construction although my specific improvement does not necessarily require that the opposite ends of the body 5 be provided with exactly identical construction.

As shown in the drawing, the ferrule, as 7,

includes a portion, as more particularly shown in Fig. 2. which surrounds body 5 and is rigidly attached thereto in any approved and well known manner, as by forming an internal thread upon the ferrule and an external thread upon the body In the drawing I have illustrated the ferrules attached as by rivets 8 passing through both the ferrule and the body. In the particular form of ferrule selected the outer end is provided with an external screw thread 9 formed on slightly reduced portion of the ferrule. The thread 9 is stopped a little short of the shoulder 10 for a purpose to be hereinafter explained.

The ferrule, as 7, has an end face 11 and is formed with a web 12, best shown in Fig. 3. This web may be of any desired form but preferably includes faces forming an aperture 13. This aperture 13, in the particular form of construction shown, includes parallel side walls 14 and 15. By such construction of the web an aperture in the web of proper shape is formed for receiving a substantial square or rectangular body which when received within the aperture is prevented from turning.

In my construction a collar or flange 18 is received and fits within the aperture in the web 12 about midway the thickness of the flange, as best shown in Fig. 2.

By the construction of terminal 4 and flange 18 as hereinbefore described, and as is more particularly seen by reference to Fig. 4, the flange 18 will fit into the recess or aperture of the ferrule web 12 and the shoulders 23 and 24 of the terminal will bear against the face of the web 12. The collar 18 being retained on the terminal by the upsets and and fitting into the aperture in the web 12 will prevent the terminal from turning and the shoulders 23 and 24 will prevent the terminal from moving inwardly into the body 5.

In order to maintain the terminal 4 in the position as shown in Fig. 1 and to form a closure for the openings of the web 12 the slotted washer 25 is provided which as shown in Fig. 2 is provided with a slot 26 which allows 'the terminal 4 to pass therethrough. The

washer 25 when slipped over the terminal 4 and moved toward the end 19 thereof comes in contact with the collar or flange 18 as best shown in Fig. 2.

The cap 27 provided with an internal thread 28 is provided to cooperate with the external thread 9 on the ferrule 7. The cap 27 is provided with the flange 29 forming the opening 30. When the cap 27 is slipped over the terminal 4, the threads 28 are brought in cooperation with the threads 9 and the cap through the flange 29 is brought to bear firmly against the interposed washer 25. The cap when screwed home is illustrated in Fig. 2 and at the left hand end of Fig. 1. In the position as thus shown the washer does not contact with the end face 11 of the ferrule 7. The washer contacts with the collar or flange 18 and so holds the terminal shoulders 23 and 24 firmly against the web 12 but this contact of the washer 25 against the flange 18 due to the position of shoulders 23 and 24 in relation to the outside face of the flange 18 prevents the inside face of the washer 25 from contacting the end face 11 of the ferrule 7 so that when assembled there is always the space 31 as best shown in Fig. 2 between the washer 25 and the end face 11 of the ferrule 7. In

order to be certain that this space 31 always exists the washer 25 is made of such thickness that the cap 27 may not be screwed onto the ferrule 7 sufficiently tightly to flex the washer 25 so as to bring it into contact with the end face 11 of the ferrule.

The parts assembled are well shown in Fig. 2 which illustrates that the end of the body is completely closed insofar as direct communication with the outside atmosphere is concerned. The washer is caused to bear so firmly upon the flange 18 that gases or hot flame may escape only to an inappreciable extent at this point. The same is true of the contact between the washer 25 and the flange 29. In order for the gases generated within the body 5 by the fusing or combustion of the fusible link to escape they must flow into the space 31 and from thence into the cooperating screw threads 9 and 28 and then by a free but tortuous path but tortuous passage for the escape of hot gas and flame from the interior of the body 5.

Applicant prefers a construction in which both ends of the body 5 are similarly constructed and arranged to the end that the terminals 3 and 4 and the link 1 together with flanges 18 may be assembled as a unit and then inserted endwise of the body 5 having the ferrules 6 and 7 in place thereon. In order to provide for this applicant forms the web 12 with a large cut-away portion 36, as best shown in Fig. 3, so that the terminal as 4 with the flange 18 thereon may be passed therethrough sufficiently to allow th terminal 1 to be moved sideways into posi tion as shown in Fig. 3. The dotted line position shows the position of the terminal 4 and flange 18 after it has been passed endwise through the ferrule 7 and body 5, but before it is moved sideways.

Although applicant has illustrated a preferred embodiment of his invention and described the construction and principle thereof, nevertheless, it is to be understood. that i the form selected is merely illustrative but does not exhaust the possible physical embodiment of means underlying the invention.

This application is a continuation of applieants copending application Serial No.

117,403, filed June 21, 1926, for Refillable electric fuses.

What is claimed as new and is desired to secure by Letters Patent of the United States,

1. A refillable electric fuse, comprising a casing, metallic ferrules fixed upon the ends of the casing and having inwardly projecting ledges and an opening between said ledges in the ends thereof, a fuse element, knife-blade terminals fixed to the ends of the fuse element, a plate carried by the knifeblade terminals adjacent to and extending within and beyond the inner edges of the knife-bladeterminals and projecting beyond the sides thereof, the ends of said plate lying within the opposite edges of the knifeblade terminals and affording supporting feet on said knife-blade terminals adapted to engage the inwardly projecting ledges of the ferrules with the plates extending'within the openings in said ferrules and projecting outwardly beyond said ledges, a slotted washer fitted upon said knife-blade terminals and engaging said plates, and an end cap fitted upon said ferrules and engaging said washers to force said plates inwardly to hold the support feet on. the knife-blade terminals in engagement with the ledges.

2. A refillable electric fuse, comprising a casing, metallic ferrules fixed upon the ends of the casing and having opposite inwar ly projecting flanges, with stepped edges, forming an opening with a narrowed central portion in theends of the ferrules, a fuse element, knife blade terminals secured to the ends of said fuse element, a plate car- 'ied by and extendingbeyond the sides and within the edges of said knife-blade terminals and adapted tobe moved laterally into the narrowed portion of the openings in said ferrules, projections on the knife-blade ter minals extending beyond the ends of said.

plate adapted to seat upon the inwardly projecting flanges of said ferrules with the plates extending outwardly beyond the flanges, and means fitted upon the terminals and engaging, the ferrules for forcing the plates into the narrowed portions of said opening and holding the projections upon said flanges, to lock the parts in place.

3. A refillable electric fuse, comprising a casing, exteriorly scrcwthreaded ferrules li ed upon the ends of the casing and hav- 1 g opposite inwardly projecting flanges with stepped edges formin an openi. with the narrowed central portion, with straight sides, in the ends of the ferrules, a fuse ele-- ment, knife-blade terminals secured to the ends of the fuse element, a substantially rectangular plate fixed to and projecting from the sides of said terminals and within the inner edges thereof acapted to be moved laterally into the narrowed portion of the opening in said ferrules, projections on the knifeblade terminals extending beyond the ends of said plate adapted to seat upon the inwardly projecting flanges of said ferrules with the plates extending outwardly beyond the flanges, and means fitted upon the knifeblade terminals and engaging the plates thereon and the screwthreaded ferrules for forcing the plates into the narro ed portions of said openings and holding the projections upon said flanges.

l. A refillable electric fuse, compri casing exteriorly screw hreaded, metallic ferrules fitted upon the ends of said casing, and having opposite inwardly projecting ledges with stepped edges forming an opening having a narrowed central portion in the ends of the ferrules, a fuse element, knife-blade terminals detachably secured to the ends of the fuse element, and plates secured to the knifeblade terminals and extending beyond the sides and within the edges of the knife-blade terminals, the projecting ends of the knife-blade terminals affording projections adapted to eng e the ledges for supporting the fuse-elemem c casing with the plates extending outwar y beyond the ledges, the said fuseele1nent an its attached knife-blades and plates adapted to be assembled lengthwise in the casing and through the openings in the ferrules and moved laterally to bring the plates into the narrowed portions of the openings therein,

and the projections of the knife-blades overlying the inwardly projecting ledges, and means fitted upon the knife-blades and engaging the ferrules for forcing the plates inwardly in said narrowed portions of the openings and the projections into engagement with the ledges for holding the part: in place.

5. A refillable electric fuse comprising a casing, metallic ferrules fitted upon the ends of said casing, and having inwardly projecting flanges at their outer ends, and opening at one side of the ferrules merging into acentral narrowed portion between said flanges, a fuse element, knife-blade terminals having reduced shanks detachably connected with said fuse element, metallic plates fixed to the shanks of and adjacent to and of less length than the width of and within and be yond the inner edges of the knife-blade terminals to afford projecting lugs for the knifeblade terminals, said fuse element and its attached knifeblade terminals and plates adapted to be assembled lengthwise in said casing by passing the knife-blade terminal and attached plate at one end thereof through the openings at one side of the ferrules and moving the knife-blades laterally, to position the plates in the narrowed central portions of the openings, with the lugs overlying the flanges, a slotted washer fitted upon the knife-blades and engaging the plates thereon, and screwthreaded end caps fitted over said knife-blades and engaging said plates and ferrules for forcing the plates into the narrowed portions of the openings and the lugs into engagement with the flanges to lock the parts in place.

6. A refillable electric fuse, comprising a casing, metallic ferrules fitted upon the ends of the casing and having inwardly project-- ing flanges at their outer ends, an opening at one side of the ferrules merging into a central narrowed portion between said flanges, a fuse element, knife-blade terminals having reduced shanks fixed to the ends of the fuse element, plates fixed upon said shanks adjacent to the inner ends of the knife-blades and extending beyond the sides and within the edges of the knife-blades and within and beyond the inner ends thereof to afford supporting lugs, said fuse element and its attached terminals and plates adapted to be assembled lengthwise in said casing through the openings at one side of the ferrules and moved laterally of the casing to position said plates in the narrow-ed portions of the openings with the supporting lugs overlying the flanges and the plates extending beyond the flanges, a slotted washer fitted upon the knife-blades and engaging the plates thereon, and screwthreaded end caps fitted over the terminals and engaging said washers and ferrules for forcing said plates into the narrowed portions of said openings and the supporting lugs into engagement with the flanges to lock the parts in place.

7. A refillable electric fuse comprising acasing, metallic ferrules fitted upon the ends of the casing and having inwardly projecting flanges at their outer ends, an opening at one side of the ferrules merging into a central narrowed portion between said flanges, a fuse element, knife-blade terminals fixed to the end of the fuse element and having reduced shanks and undercut notches adjacent to said shank, slotted plates fixed upon said shanks adjacent to the edges of the knifeblades and extending beyond the sides of the knife-blades and having their ends inset into the notches of the knife-blades to afford supporting lugs extending inwardly beyond the outer surface of said plates, said fuse element and its attached terminals and plates adapted to be assembled lengthwise in said casing through the openings at one. side of the ferrules and moved laterally of the casing to position said plates in the narrowed portions of the openings with the supporting lugs overlying the flanges, a slotted washer fitted upon the knife-blades and engaging the plates thereon, and screwthreaded end caps fitted over the terminals and engaging said washers and ferrules for forcing said plates into the narrowed portions of the openings and the supporting lugs into engagement with the flanges to lock the parts in place, the said lugs holding the plates beyond the flanges to thereby maintain contact between the slotted Washers and said plates and a substantially tight seal between the slotted plates and the slotted Washer.

FRANK C. LA MAR. 

